The present invention relates generally to medical devices and more particularly to a stent.
One type of intraluminal medical procedure that uses a stent-graft is the TIPS procedure. TIPS refers to a transjugular intrahepatic portalsystemic shunt that is used to treat portal hypertension that typically occurs due to chronic liver problems, such as cirrhosis. Cirrhosis of the liver may occur due to alcohol abuse or hepatitis B and C, and results in scarring of the liver tissues which reduces blood flow through the liver. Because of the reduced blood flow through the liver, blood pressure can build in the portal vein system, which can cause a number of problematic symptoms.
In order to relieve pressure in the portal vein system, a TIPS procedure involves placing a shunt in the liver between a portal vein and an hepatic vein. As a result, blood flowing through the shunt effectively bypasses the obstructed liver tissues. While this treatment does not cure the underlying liver problems that cause portal hypertension, it does diminish the side effects caused by portal hypertension and can improve a patient's quality of life and possibly extend a patient's life until a liver transplant can be performed.
In a conventional TIPS procedure, access to the patient's venous system is usually gained at the neck into the internal jugular vein. A catheter and needle are then threaded through the venous system to the inferior vena cava and an hepatic vein. From the hepatic vein, the physician penetrates through the tissues of the liver with the needle until the needle intersects a portal vein. A balloon is typically used to inflate the passageway created between the hepatic and portal veins, and a stent-graft is implanted into the passageway to maintain fluid communication between the portal vein and the hepatic vein.
Stent-grafts used in TIPS procedures typically have an uncovered portion and a covered portion that are designed, respectively, to allow blood flow through the stent wall and isolate blood flow within the lumen of the stent. For example, it is usually desirable to place the stent-graft so that a portion of the distal end of the stent-graft extends into the portal vein. This portion of the stent-graft is preferably uncovered so that blood can access the inner lumen of the stent and pass through the passageway of the shunt, but also so that blood can flow past the shunt and through the liver tissues to utilize any remaining liver function that may exist. However, the proximal portion of the stent-graft that extends through the shunt passageway is preferably covered to seal the blood flow within the lumen of the stent. This is important because the surrounding liver tissues would quickly stenos and close the shunt if a non-covered stent were used, and also because the shunt will typically intersect bile ducts between the portal and hepatic vein which would cause blood flow through the stent to quickly clot if the blood were exposed to the bile ducts.
In order to ensure that the stent-graft in a TIPS procedure performs successfully, it is important that the transition between the uncovered portion and the covered portion be accurately located at the junction between the portal vein and the shunt. For example, if the uncovered portion is positioned partially within the shunt, the opening of the shunt could stenos and obstruct blood flow into the shunt. Also, the portion of the shunt that is exposed through the uncovered portion of the stent can cause blood clotting. Conversely, if the covered portion of the stent is located within the portal vein, the covered portion can block blood flow into the lumen of the stent and past the stent-graft into the liver.
Accordingly the inventor believes it would be desirable to provide a stent with arms for positioning the stent at a junction between two passageways.